R.H. Traquair — On a New Carboniferous Fish from Airdrie. 555 



ribs whose inner structure has been laid open. Of spinous 'processes, 

 some are seen of course scattered among the ribs in the front of the 

 specimen, and where the ribs cease posteriorly, the skeleton is repre- 

 sented by a pretty confused mass of spines and interspinous bones. 

 As to the spinous processes themselves, their remains are too much 

 broken and jumbled together to allow of any description of their 

 form, or of that of the vertebral arches from which they spring. 

 They seem to have been very strong and powerful, and some of their 

 fragments measure 1^ inches in length by \ inch in diameter ; they 

 are also hollow, with an internal tubular cavity filled with carbonate 

 of lime. Many interspinous hones, or fin-supports, occur scattered 

 about, these are laterally flattened, expanded at both ends, and narrow 

 in the middle ; some of them, varying from f to 1 inch in length, 

 are seen isolated and well defined in form, lying opposite the portion 

 of the dorsal fin shown in the specimen, but none in actual contact 

 with it. 



Dorsal fin. — This commences distinctly to be seen at 5 inches from 

 the front of the specimen, and thence extends back for the whole of 

 its length ; but I doubt whether the actual commencement is seen. 

 The portion of the fin exhibited is 10 ^ inches long, and one inch 

 broad near its commencement, attaining, however, a breadth of two 

 inches posteriorly. The fin consists of very numerous closely set 

 rays, converging towards their attached extremities into small sets 

 of 3 or 4, apparently resulting from the division of one original 

 individual, though unfortunately the actual proximal commencement 

 of the rays is not clearly shown. Their direction is very oblique to 

 the dorsal margin of the body, and this obliquity increases the 

 further back we go, till in the broad part of the fin, behind where 

 the dorsal margin falls away towards the tail, it is such that each 

 ray must have attained 4 inches in length. Towards their extremi- 

 ties the rays are seen to have split up into very minute divisions, 

 with distinct though proportionately distant transverse articulations. 

 No transverse articulations occur, however, in the first part of their 

 length, varying from 1^ inches in the front of the fin to 2i inches 

 in the longer rays behind. 



Conclusion. — The fish, whose fragmentary remains have been just 

 described, evidently belongs to a new species ; but, unfortunately, 

 the evidence as to the genus to which it ought to be referred is by 

 no means complete, as the specimen shows no head, nor any fins 

 except a portion of the dorsal. It is very evident, however, that it 

 belongs to the family Plianeropleurini, and I consider that it is on 

 the whole safer to refer it to the Carboniferous genus TJronemus, 

 Agass., than to any other. The only other species of this genus 

 which is as yet known is the TJronemus lobatus, Agass., of the Burdie- 

 house Limestone, a very small fish, none of the known specimens of 

 which have exceeded 7 inches in length. I propose then, provision- 

 ally at least, to bestow upon the fish from Airdrie the specific name 

 of Uronemus magnus. 



